Generally your lens will come with the hood that ws made for it (at least it did with all my Nikon lenses. If that was not the case you might be able to order it somewhere. Besure to get the proper lens hood though because lens hoods especially with wide-angle lenses that are not made for the focal-kength lens they are on can cause vignetting.
I tried the Sony website and could not find any lens hood being listed as available seperately from the lens. If your lens did not come with a hood there might not be a Sony hood available for it. I know you can get rubber hoods fairly cheaply from Ritz Camera or at least I used to get them all the time because the ones I bought for my Bronica were so cheaply made that they only lasted 2-3 weddings but they cost so little that it was not an issue to buy them.
By the way I did a quick search on Amazon for "sony lens hood" and came up with (among other things) this: